Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: more on : IEEE 802.3 Requirements

In response to your message below, I wanted to remind you that one of the
advantages of a WWDM (Wide WDM) approach to 10GbE is to support the
160MHz-km MMF installed base.  WWDM using 4 wavelengths should support
approximately 300 m of the installed base of MMF.  


-----Original Message-----
From: Michael M. Salzman [mailto:msalzman@xxxxxxx]
Sent: Wednesday, May 19, 1999 11:30 PM
To: stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
Subject: more on : IEEE 802.3 Requirements

Hi Ed,

I am uncomfortable as a standards body telling people that they should use
fiber X to reach 300M and to then say, well if you want to run over
installed base, try it and see how far you get.  We know that serial streams
at 10G or thereabouts, on 160MhzKm fiber will not even reach 100M.
Realistically, some fibers out there will go to 150 or more.  But, consider
that the buyer will go to some trouble to set up a new, expensive trunking
facility and they will schedule some down time to deal with it, interrupting
many users in the process.  It seems to me unlikely that a project manager
in that position will want to rely on unknown properties of of current
cable.  Furthermore, as the plant continues to age, what parameter will
fail, how and when?  We already know that existing fiber is simply far from
capable of supporting the new rates.  It is not a matter of close but no
cigar.  It is more than an order of magnitude difference in quality of the

Therefore, my sense is that the project owner will decide up front whether
to replace the fiber or not.  My guess is that on main trunks, they will
replace them with single mode.  In many new applications they could put in
high performance multi mode.  In impulsive applications (which will be
scarce in the beginning) they will simply try to see if they can live with
the installed base.  If a MAS or CWDM PMD is available, they might simply
decide to try that one for their installed base applications.

To your point about educating the masses of installers, experience teaches
that it takes on the order of 5-10 years to inculcate an appreciable
quantity of them about the stringent aspects of installations.  How many of
them really know the differnces between cables and various kinds of fibers?
how many still do not know the total panoply of procedures and equipment to
install Cat5 correctly?  I think we want our technology in the market before
much of this knowledge will become commonplace, therefore we need to
enunciate a clear set of requirements in a black and white manner for these
people to follow.


> -----Original Message-----
> From: Chang, Edward S [mailto:Edward.Chang@xxxxxxxxxx]
> Sent: Wednesday, May 19, 1999 06:29
> To: msalzman@xxxxxxxxxx; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: IEEE 802.3 Requirements
> Mike:
> You are right, I agree with your reasoning.
> The key points we are addressing is we should be flexible, convenient to
> users, easily adaptable by market.  The rest of the headaches are upon
> technical people(us) to make it happen.
> We will allow the installed bases to be used without modifications at a
> shorter distances -- perhaps, 100, 200, or even 300 meters?, then
> we can add
> the extended distance with the new super fiber for longer
> distances at added
> material and installation costs.
> We have to device to products to make sure all levels of users are
> affordable.  One area I do not quite agree with you is that: quote, "the
> case of 10 Gig, due to its novelty and likely expense, I think we can lay
> down new standards for fiber to support it, and customers would go along
> with the concept".  There are some users will fit into your expectation;
> however, there are many will take a bite, only if it is truly
> cost-effective, but not novelty.
> We do not have to worry about DMD, or very low-BW cables, which you agree.
> When users has problems with bad cables, they will find out by excessive
> errors or re-tries.  They will call field servicemen to fix for
> them.  Those
> servicemen will understand how to identify the bad cables to be
> removed from
> service.  All we have to do is to educate field servicemen how to identify
> them.
> -----Original Message-----
> From: Michael M. Salzman [mailto:msalzman@xxxxxxx]
> Sent: Wednesday, May 19, 1999 5:32 AM
> To: stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> Subject: RE: IEEE 802.3 Requirements
> Hi Bruce, Ed, et al,
> My experience is that on average no installer tests fiber for any thing
> other than connectivity.  To imagine that these fellows will carefully
> follow some timeconsuming and deliberate procedure to check out
> the cable is
> wishful thinking.  You are right that DMD is an innate 'feature' of most
> installed base fibers.  The ethernet community only recently
> discovered its
> ubiquity and impact.  Nevertheless we can expect the vast
> unwashed masses to
> blithely ignore any special handling and testing requirements untill their
> installation fails to come up and then they will search for causes.
> In the case of 10 Gig, due to its novelty and likely expense, I
> think we can
> lay down new standards for fiber to support it, and customers
> would go along
> with the concept.  For those stubborn souls who insist on deploying the
> technology on existing fiber, I think the 10GEA can develop
> recommended test
> procedures and recommended equipment sets, and perhaps work with BICSI to
> develop a "gigabit technician" certification program.   If we do
> not address
> this prosaic aspect of our industry we are doomed to seeing more trial and
> error installations.
> Mike.
> > -----Original Message-----
> > From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> >  Behalf Of Chang,
> > Edward S
> > Sent: Monday, May 17, 1999 06:36
> > To: Bruce_Tolley@xxxxxxxx; Chang, Edward S
> > Cc: Thomas Dineen; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> > Subject: RE: IEEE 802.3 Requirements
> >
> >
> >
> > Bruce:
> >
> > The 62.5 um fibers have been used for over 15 or 20 years.
> > However, we just
> > started paying attention to the DMD fibers two years ago.
> Because of the
> > small DMD population, industry did not paying attention to it.
> > In fact, the
> > DMD fibers have been with us since the graded index fibers were
> > introduced.
> > DMD fibers are defected parts like any other products having
> > defected parts.
> >
> > In the past, the MM fibers, particularly 62.5 fibers, were only
> used with
> > LED sources over-filing the fibers, which is hardly capable of
> creating a
> > DMD results except low bandwidth.  It was until GbE requiring laser over
> > 62.5 um fiber, the DMD has not been identified as a detrimental
> > problem.
> >
> > The fiber vendors do not characterize "DMD" as one of the parameters in
> > their commercial specification due to its very small, negligible
> > population.
> > As a result, no one really pays attention to verify it, unless an
> > experienced engineer is purposely looking for DMD fibers.  Some
> time, just
> > to identify DMD fibers from the waveforms is not a simple job.
> >
> > Ed Chang
> > Unisys Corporation
> > Edward.Chang@xxxxxxxxxx
> >
> >
> > ----Original Message-----
> > From: Bruce_Tolley@xxxxxxxx [mailto:Bruce_Tolley@xxxxxxxx]
> > Sent: Friday, May 14, 1999 5:29 PM
> > To: Chang, Edward S
> > Cc: Thomas Dineen; stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
> > Subject: RE: IEEE 802.3 Requirements
> >
> >
> >
> >
> >
> > Ed:
> > As far as I know, hardly any "DMD fibers" have been identified to date.
> >
> > Bruce
> >
> >